Luximeter.



W. DA. RYA

LUXIMETER;

APPLIOATION FILED 001. 15, 1909.

Patented July 5,1910.

3 SHEETB8HEET 1.-

Inventor Walter DfLRyan,

Witnesses w. DAQ RYAN.

LUXIMETER, I AIPLIOATION FILED OCT. 15, 1909.

3 SHEETS-SHEET 2.

Inventor Z Walter D'TLgan Witnesses:

W. DA. RYAN. LUXIMETER.

APPLICATION FILED 0(JT.15 1909.

963,0?2, Patented July 5,1910.

3 SHEETS-SHEET 3.

Eu 5; We;

Witnesses: 56 Inventor; 7 Z Walter Dff Ryan,

%% i Hls flttorneg.

WALTER ZDA. nYA'iq, orwernnrown, scum DAKOTA, assrenon T0 GENERAL ELECTRIC'COMPANY, A CORPORATION or NEW-YORK.

LUXIMETER.

Specification of Letters Patent.

Patented July 5, i910.

Applicationfiled October 15, was. 'Serial iresaa'rss.

To aZZ whom it may concern:

Be it'known that I, WALTER DA. RYAN, a,

subject of the Kingof Great Britain, residing at 'Watertown, county of Goddington, State of South Dakota, have invented certain new and useful Improvements in Luximeters, of which the following is a specification.

My invention relates to photometers and similar devices for measuring or comparing the intensity of light or of illumination, andparticularly, to devices which may be called luximeters and by means of which the intensity of illumination at any point may be determined in terms of some standard'unit. Various forms of photometers have been proposed and used, but many of them are bulky and diflicult to' transport; must be used by an operator of great skill and experience in .order to secure reliable results and are particularly subject to error when used to determine the intensity of illumination on account of errors inherent in the plates or surfaces exposed to the illumination which is to be measured.

' The object of my invention is to produce a compact, accurate direct reading and easily operated portable photometer or luximeter,

by means OfWlliCll accurate determinations of the intensity of illumination may be made; in which the amount of light transinitted to the photometric or light comparing device is directly proportional to the illumination upon aplane surface at a point at which the photometer is placed, in which the comparison lamp may be accurately adjusted to give a definite amount of light; in which all of the operating parts of the instrument are inclosed in a casing and are suspended in their proper relative positions on the cover of the casing, so that when the cover is removed all parts ofthe instrument may be easily examined and adjustedyand in which the various parts of the instrument are so related to the eye piece that, the operator can see the scale and manipulate the various parts of the instrument with a maximum of ease and convenience.

My invention'will best be understood in connection with the accompanying drawings, Which show one ofthe various forms in which it may be embodied and which form I have named a luximeter.

. In the drawings, F gure 1 1s a plan V18W' of the instrumentready for use; Fig. 2 is' a ,line 3-3 of Fig. 1; F

- mitted to the vertical section along the line 2-2 of Fig. 1; Fig. 3 is avertical cross-section along the ig.-4 is a vertical cross section along the line H of Fig. 1; Fig. 5 is a view of thepreferred form of photometric device secured in fixedrelation to the preferred form of light transmitting device by means of which light proportional to the intensity of illumination is transphotometric device.

.The particular form of instrument shown in the drawings is acompact and easily portable device with the various parts contalned 1n and protected by a casing or box 10, provided with a removable cover mination is to be measured, the box is placed inany desired position and light directly proportional to the intensity of illumination at the 'point occupied by the instrument and in the plane of the cover ll of the box is transmitted to the interior of the box by means of a light transmitting device mount- 11, de-- tachably secured to the box. When the illued in an opening in the cover 11 and consisting of a translucent block 12 having a curved surface which projects through the cover of the box, as shown in Figs. 2, 4 and 5, and through which light is transmitted to the interior of the box. The surface of the translucent block 12 isapproximately spherical in shape and by properly shaping the surface of the block the light transmitted by the block 12 may be made directly pro.- portional to the intensity of illumination. In general work, the intensity of light incident upon a given surface, commonly called the test surface, is the only quantity which it is practical or even desirable to measure and in'an accurate instrument the light intensity which is .measured must be strictly proportional to the light incident upon the test surface. Accurate results would be obtained by observing a plane which is a perfect diffuser of light, since the light inci- ,dent upon such a surface at any angle is credited only wit-h its true intensity. There is no available surface which accurately meets these requirements and the best method is to use some form of translucent test surface and to observe the transmitted light from a point directly beneath that surface. A given horizontal surface is illumi-- nated not only by rays of light at right angles to the surface, but also by rays of light which strike the surface at all inclinations from the vertical to the horizontal, and experience has shown that the light transmitted through a flat test surface of translucent material is not-a true measure of the illumination to which the surface is exposed, because if a plane diffusing surface be illuminated by rays of light which form only a small angle with the surface, and. thereby a given intensity of illumination is comes smaller. In my invention this source of error is avoided and the light transmitted through the block 12 obeys Lamberts law of the cosines with reference to intensity of illumination produced by light incident at any inclination and from any direction upon a plane surface occupying the position of the block 12, which is practically the plane of the cover 11.

In the preferred construction which is shown in detail in the drawings, the curved surface of the block 12 is made substantially spherical and the light transmitted to the interior of the box 10 through the block 12 is rendered proportional to the illumination 'by shading a portion of the surface of the block 12 by any suitable device, such as a ring 13 mounted concentric with the block and projecting perpendicularly from the cover 11. As clearly'shown in the drawings,

the upper edge of the ring is serrated for the purpose of accurately adjusting the amount of light which will fall upon the curvedsurface of the block 12 and by properly proportioning the height of the ring and the shape and number of serrations in the upper edgeof the ring, the required correction can be accurately made. Other means may be used for shading the edges of the light transmitting surface of the block 12, but the ring shown in the drawings and above described has been found to give good results in practice and is the preferred form of construction.

The light transmitting block 12 is mounted in the opening in the cover 11 by means of a supporting ring 14: and the light trans mitted through block'12 may be measured by any suitable photometric device mounted comprising a cubical block of translucent material divided by a diagonal slit or diaphragm 16, one side of which is illuminated by the light transmitted throughtheblock 12 and the other side of which is illuminated by the light from a comparison lamp in the box 11. The slit 16 becomes invisible when the'illumination on the two sides of the slit metric device has one surface covered by an opaque covering 17 provided with a circular opening so; related to the photometric device that the circular opening is bisected by the slit or'diaphragm 16. As best shown in Fig. 4, in whlch the photometric device is shownin section, one surface'of the photometric device receives light from-the trans lucent block 12, while another surface l8 is exposed to the comparison lamp,'and on looking at the observation surface of the photometric device the observer sees a disk, one half of which is illuminated by the light from the block 12 and the'iotherhalf' by light from the comparison lamp.

observation surface of the photometric device, and thereby compare the illumination on one side of the slit or diaphragm 16 with thatof the other side,-some suitable form of eye piece is provided in one end of the box and. in order to make the photometer more structed tofold into a recess in the box 10 when the-photometer is not in use, and to be servation is to be taken. In the particular instrument shown in the drawings, a recess is formed in one end of the box 10 by a partition 19 which has an opening in alinement with the observation surface of the photometric device when the cover 11 is in place.

\ end to the walls of the opening in the partition 19 and is connected at the other end to a sliding head 21 which has an opening or eye piece 22 through which the photo metric device may be observed, The sliding head 21slides upon andis supported by a door 23 which is hinged to the'box 10 and closes the recess .in the end of the box 10 when the bellows is folded up. The door is supported in its extended position by supprovided near the other end with slots which box 10. After the observation is taken the head 21 is move to the left, the bellows collapses and both the bellows and the sliding head 21 are received in the recess, whereupon the door 23 may be lifted into' osition to close the recess and isthen he d by a suitable latch 25 which engages the door and is controlled by means of a push button 26 extending through the cover 11.

In the particular arrangement shown, where the eye piece 22 is below the photo metric device, inspection of the photometric device is facilitated by means of an observation mirror 27 pivotally mounted in the sliding head 21 in such a relation to the eye piece 22 and to the photometric device; that border that the observer may inspect the.

An extensible bellows 20 is secured at one ports 24 pivoted-at one end to the door and is equal. As best shown in Fig. 5, the photocompact the eye piece is preferably conextended to the proper position when an obslide over pins secured to the walls of the the translucent block 12 is determined in terms of some standard unit by exposing the surface 18 to a light of knownqintensity, which may be obtained in various ways, preferably by means of a comparison lamp and a shutter mounted between the lamp and the photometric device to vary the amountof light received by the photometric device fromthe comparison lamp. The intensity of illumination of the surface 18 is controlled by any suitable form of shutter, such asthe concave cylindrical shutter 29 shown in elevation in Figs. 2 and 3, and in section in Fig. 4. As best shown in Fig. 4, this shutter is in the form of a cuphaving-a comparatively deep rim 30, on which is mounted a scale 31. in registry with a Window 32 in'the cover'll and through this window the scale may be observed and the angular position of the shutter accurately determined.

The amount of light received by the surface 18 of the photometric device is varied by varying the angular position of the shutter which has a tapered slot 33 in the bottom in a position to register with the surface 18 in different angular positions of the shutter. Vhen the shutter is in the position shown in Fig, 2 the maximum amountof light is received by the surface 18, while if the shutter is given little more than a half revolution in a counterclockwise direction, the amount of light received by the surface 18 is-reduced to a minimum and desired may be cut off entirely by the solid portion ofthe bottomcf the shutter 29.

The shutter 29 is mounted for angular rotation upon any suitable support, such as a shaft 34 rigidly secured at one end to the shutter and having at the other end spring fingers 35 which normally .grip a shutter, operating handle 36 inserted through an opening in the side ofthe box 10 to engage the spring fingers 35. The shaft 34 is suitably j ournaled in a pedestal 37 fastened to a base plate 38 which in turn is suspended from the cover 11 by means of posts 39 and since the base plate 38 and all the parts mounted on it are out of contact with the walls of the casing of the box 10, thecover and all parts attached to it may be lifted from the box if'the shutter operating handle 36is moved out of engagement with the" spring fingers 35. I

The lightdirected' upon the surface 18 andcont-r'ol'led by the shutter 29 may be derivedfro'm any suitable source preferably; an electric comparison lamp 40 carried on a block 41 which is detachably secured to a pedestal 42 on the base plate 38. When the comparison lamp 40 is in position, it is practically concealed in the concave orv cupshaped shutter 29; the rim 30 of the shutter being wide enough effectually to shield the eye piece-22 from the lamp so that the inspection of the photometric device is not in-' terfered with by light from the comparison lamp. In'o'rder to further guard against the comparison lamp illuminating the inte rior of the box 10 the lamp is surrounded by an opaque casing 43 which nests within the concave shutter 29 and which has in the wall adjacent the bottom of the shuttel an opening 44 through which light passes from the comparison lamp and thence through the slot 33 of the shutter to the surface 18 of the photometric device. 7

In order that the comparison lamp may I give an approximately uniform amount of light, it is necessary that-the amount of current flowing through it be accurately known. An electric measuring instrument such as an ammeter 45 is suspended from the cover 11 of the boX 10 with its scale plate 46 projecting through the cover of the box and fac-- ing the eye piece 22 so that the operator without moving from his position can glance at the scale plate 46 and see the amount of current flowing through the comparison lamp. The ammeter 45 is connected in series with the comparison lampand with any suitable source of current, such as dry cells 47 suspended from the cover 11 and connected in series by means of .leads 48, as

shown in Fig. 1. The circuit including the comparison lamp, the measuring instrument,

and the dry cells is completed through a rheostat 49 suspended from the cover 11 and having an operating handle 50 which projects through the cover in a position where it may be conveniently reached by the operator at the eye piece 22. The-circuit through the lamp is controlled by a switch 51 having a handle projecting through the cover 11 adjacent the operatin handle of the rheostat and normally tending tomove to the open position so that the circuit through the lamp is closed only when the switch 51 is closed by the operator. The

comparison lamp is' therefore lighted only forthe few moments required to make an observation and is automatically extinguished as soon as the operator releases the switch.

The photometric device, the comparison lamp, the shutter, the measuring instrument and its accessories all constitute a light comparing mechanism which is suspended from the cover 11 out of contact with the walls of the box 10 and which may all be removed from the, box by detaching the cover 11 and lifting it away from the box. The operator is therefore enabled to inspect and to adjust all parts of the light comparing mechanism and to observe their operation in. the same relation to each other which they will have when in place in the box 10, and therefore the photometer can be rapidly and accurately adjusted.

The comparison lamp is calibrated at intervals by comparing itwith any suitable standard lamp. A calibrating tube- 52 mounted in the side of the box-in alinement with the photometric device and normallyclosed by the cap 53 admits light from a standard lamp to'the one side of the photometric device while the light from the com{ parison lamp is admitted to the other side and the comparison lamp may then be quickly adjusted to givea light Which-bears any desired relation to the standard light.

The operator may useother photometric devices than the particular screen shown and by introducing the light which is to be measured through the calibrating tube 52 instead of through the light transmitting block12 a screen of thewell known Bunsen type may be used if desired, but for general work and for accurate determination of illumination the type of photometric device shown and the light transmitting block 12 is preferred. My invention may be embodled in many other forms than that-shown and described i and I therefore do not limit myself to the tensity of light receivedby a plane surface -inthe positionof said block.

7 2. A light transmitting device for te tometers com rising a translucent -b ock having a sur ace for receiving the light to be} measured and means whereby said surface receives less light neai" the edges than at the center and thereby the light trans mitted' through said block is rendered proportional to the intensity of light received.-

by a plane surface in the position of-said block.

3, A light transmitting device for photometers comprising a translucent block having a surface for receiving light to be -.II lB%LS- ured, and means cotiperatlng with said surface to render' the light transmitted by," said I curved surface which projects fromv saidbase block proportional to the intensity of light received by. a plane surface in the position of said block.

4:. A light transmitting device for phoing a surface which receives the light to be measured and is shaped to transmit light proportional to the intensity of illumination of a plane surface placed in the position of said block.

, -5. A light transmitting device for pho- "tomet ers comprising a translucent block hav tometers comprlsing a translucent block having a surface for receiving the light to be measured and means mounted near the edge of said surface to shade a portion thereof from light of which the angle of incidence upon said surface exceeds a predetermined amount.

6; A light transmitting device for photometers comprising a translucent block having asurface for" receiving the light to 'bQ measured, and a ring mounted concentric with said surface and having itsv upper edge shaped to shade a portion of said surface and thereby control the amount of light re- ;ceived by said surface.

7. A light transmitting device for hotometers comprising a translucent blockav ing a spherical surface for receiving the light to be measured, and means for con trolling the amount of light received near the'equator of said surface.

tometers comprising a flat opaque base having an openingthrough it and a translucent block'mounted in said opening, said block having a curved surface which projects from 8. A light transmittingdevice fOI PhO- said base to' form a hemispherical light receiving surface.

9. A lighttransmitting device for photometers comprising a flat opaque base with an'opening through it, a translucentblock having a curved surface and mounted in said opening with said surface projecting from said base to form a hemispherical light :receiving surface, and means for controlling the amount of light received by said surface at predetermined angles to said base.

10. A light transmitting device for'photometers comprising a flat'opaque base with anopeningthrough'it, a translucent block mounted in said' opening and means proj ect-,

ing per endicularly from said base near the edgeo' said opening to shade a portion of said surface.

-11. Adight transmitting device for photometers comprising a flat opaque base with an opening through it, a translucent block mounted in said opening and a mug mount-- ed to project perpendicu arly from said base to surround said block near the edge thereof. 12. A- light transmitting device for photometers having aflat opaque base with an opening through it, a translucent block mounted in said opening; and having a to form a hemispherical light receiving surface, and a 'ring. mounted to project .perpendicularly from said base and to surround '25 I 15. A photometer comprising a comparieespvs said surface near the edge thereof, said'ring --having its upper edge serrated .to regulate 1O proportional to the intensity of illumination of a plane surface in the position of said block and an observation surface which permits the illumination of the other two surfaces to be compared.

14.- A photometer comprising a box, a comparison lamp in said box, and a hotometric screen comprising a trans ucent block mounted in said box with one surface exposed to said lamp, a second curved sur -face projecting through the walls of said box to form a hemispherical light receiving surface, and a third surface in a position to permit observation and comparison of the illumination of the other two surfaces.

, son lamp, a photometric screen exposed to said lamp and to the light to be measured,

and' a movable shutter mounted between said lamp" and said screen and having a tapered slot in registry withsaid lamp and screen.

16. A photometer comprising a comparison lamp, a light comparing screen exposed to said lamp and to the lightto be measure'd,

and a rotatable shutter extending between.

said lamp and screen and having a tapered slot therein to register with the lamp and screen in differentangular positions of said shutter.

17. A photometer comprising a box, a photometric device mounted in said box to receive the light to be measured, an eye piece in the Wall of said box whereby said photometric device may be observed, a comparison lamp mounted in said box, and a concave shutter adjustably mounted in position to shield said lamp from the observer and havi g a tapered slot in the bottom in registry with said lamp and said device.

18. A photometer comprising a box, a photometric device mounted in said box to receive the light to be measured, an eye piece in the wall of saidbox whereby said photometric device'may be observed, a comparison lamp mounted in said box, and a circular concave shutter having a taperedslot in the bottom and rotatably mounted between said lamp. and said device in a position to par tially inclose said lamp and thereby shield it'from the observer.

19.- .A photometer comprising a photometric device for receiving the light to be meas- 'ured, a concave circular shutter having a tapered slot'in the bottom thereof and rotatably mounted with said slot in registry with said device, and a comparison lamp mounted within the concavity of said shutter and in registry with said slot.

20. A photometer comprising a box, a photometric device mounted in said box to receive thelight to be measured, an eye piece in the wall of said box whereby said device may be observed, a concave circular shutter having a tapered slot in the bottom and rotatably mounted to bring said slot into registry with said device, a comparison lamp mounted within said shutter and an opaque casing for said lamp having adjacent the bottom of said shutter an opening in registry with said slot.

21. A photometer comprising a box having a window in one wall, a photometric device mounted in said box to receive the light to be measured, an eye piece in the wall of said box whereby said photometric device may be observed, a comparison lamp mounted in said box, and a shutter rotatably mounted between sald lamp and said a device for controlling the illumination of said device by said lamp and having on its periphery a scale in registry with said window.

22. A photometer comprising an oblong box, a photometric device in said box, an eye piece at one end of said box whereby said device may be observed, an electric lampin said box adjacent said device, a shutter between said lamp and said device, an operating handle'for said shutter extending through one side of Said box, and a switch mounted on the top of said box for controlling the circuit through said lamp.

23. A photometer comprising a box, a photometric device in said box, an eye piece whereby said. device may be observed, an

electric comparison lamp mounted in said boxadjacent said device, a source of current for said lamp, and an electrical measuring instrument connected to said lamp' and mounted with its scale plate facing said eye piece.

24. A photometer comprising a box, a photometric device in said box, an eye piece whereby said device may be observed, an electric comparison lamp mounted ,in said box adjacent said device, a source of current forsaid lamp, and an ammeter connected in series with said lamp and mounted inside said box with its scale plate outside the box and facing toward said eye piece. 25. A photometer comprising a box, a photometric device mounted in said box, a comparison lamp mountedadjacent said photometric device, a rheostat connected in series with said lamp and rheostat adjustin means box.

26. A photometer comprising a box having an opening at one end, a photometric projecting through the cover of said.

device" mounted in said box adjacent said opening, a bellows secured at one end to the walls of said openin an eye piece in the other end of said he lows, and means connected with said box for supporting said eye piece in definite relation to said photometric device 1 and a mirro'r mounted near said eye piece to reflect the image of said device to said eye box, means for slidab piece.

28. A photometer comprising a box having a recess at one end, an opening in the wall of said recess, a photometric device mounted in said box adjacent said opening, an extensible bellows having one end secured to thewalls of said opening, a supporting member hinged to-the side of the y supporting the other end of said bellows on said supporting member, and an eye piece on the other end of said bellows.

29. In a photometer, the combination with a box, of a detachable cover for said box carrying light comparing means comprising a photometric device, a comparison lamp, and means for controlling the light received by said device from said lamp, all mounted on said cover and removable from said box with said cover.

30. In a photometer, the combination with a box having an eye piece at one end, of a detachable cover for said box carrying light device mounted in a position to be visible from said eye piece when said cover is in place, a comparlson lamp, a shutter between saidlamp and SHid'dBVlCB, and means for controlling the light received by said device from said lamp, all suspended from said cover and outof'contact with the walls of said box.

31. In a photometer, the combination with' a box, of a detachable cover for said box carrying light comparing means comprising a photometric device securedto said cover, an electric comparison lamp mounted on said cover, a source of current carried by said cover and means on said cover for controlling the light received by said photodevice in alinement with said observation opening, a comparison lamp, and a shutter between said comparison lamp and said device, all suspended from said cover out of contact with the walls of said box, and a detachable handle extending through said control opening to engage and control said shutter.

In witness whereof, I have hereunto set.

my hand this 14th day of October, 1909.

WALTER DA; RYAN.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

